a) Field of the Invention
The invention is directed to a method and a device for directed mounting of a measurement strip in a length measuring system by means of a mounting device.
b) Description of the Related Art
Scales made from steel strip are advantageously used not only in length measurement arrangements but also in angle measurement arrangements. These scales offer advantages over scales made from glass with respect to noncontact measurement, compact installation, and a robust, vibration-resistant construction.
In an embodiment form described in the periodical "Feinwerktechnik und Me.beta.technik", Vol. 88, 7, pages 333-338, a groove is ground into a stainless steel scale body and the actual graduation substrate, which is a thin steel measurement strip, is cemented therein. In order to reinforce the gluing, weld points are placed at the start and at the end and at determined intervals at the side of the measurement strip for a rigid connection of the latter with the substrate body. This solution is advantageous in that the substrate body and the measurement strip can be produced separately and the measurement strip can accordingly be manufactured economically in any length. On the one hand, this solution is limited with respect to the length of the scale body that can be realized and also, on the other hand, is still very expensive and complicated to mount. In addition, the scale lengths are still limited because the base body can only be meaningfully manufactured and handled up to a length of several meters.
Another way of mounting measurement strips is described in DE 689 06 881 T2. In this case, a self-adhesive steel-strip scale is aligned with the guide sequence of the slide or carriage by means of an applicator and is glued onto the machine bed or to a base body. Although this type of measurement strip mounting provides a good correspondence between the measurement strip and scanning head over the entire measuring area, the basic accuracy that can be achieved in the measuring system is relatively poor because the inherent stability of the measurement strip is relatively low and the slightest mechanical stresses or differences in tension, which are unavoidable during the gluing process, lead to impaired measurement in the scale. Further, this method has the disadvantage that exchanging or disassembling the measurement strip is very involved and the measurement strip is generally no longer usable.
Another common type of fastening for thin measurement strips consists in that the measurement strip is received along its longitudinal extension in a groove. This is described in the company brochure "NC Langenme.beta.systeme [NC Length Measuring Systems]"from Heidenhein, June 1996. As a rule, they are special receiving profiles made from extruded aluminum. However, these receiving profiles are limited with respect to the lengths that can be realized and, in addition, are also still very complicated to mount. The attainable spacing tolerances between the measurement strip and scanning head are also limited in this solution, since the flatness tolerance and position tolerance of the receiving groove in the extruded profile must also be taken into account in the flatness tolerance of the receiving surface.